The present invention pertains to a conductive oxide sintered body suitable as the electrode of a dielectric thin film memory for the likes of a DRAM or FRAM, a sputtering target formed from such a sintered body, and the manufacturing method thereof.
Conventionally, a Pt electrode has been used as the electrode of a dielectric thin film memory for the likes of a DRAM or FRAM. Nevertheless, in light of indications that the ferroelectric thin film deteriorates with hydrogen as a result of the Pt electrode catalytic activity, several conductive oxides have been proposed as a replacement for this Pt electrode. As such conductive oxide, considered may be SrRuO3, SrIrO3, CaRuO3, BaRuO3, Sr2RuO4, Sr2IrO4 and so on.
Meanwhile, although PTZ (PbZrxTi1−xO3) or BST (BaSrTi3) is being used as the dielectric material, the foregoing conductive oxides are considered to be extremely promising since they are compatible therewith in terms of the material quality and have low bulk resistance.
Nevertheless, each of the conductive oxides listed above has a problem in that the sintering density thereof is significantly low since the sinterability is inferior. With the sputtering target obtained from this kind of low density sintering target, since the pore shape in such target is of an open pore, abrasive cutting powder or the like remains during the target processing, and there is a problem in that particles are generated considerably during sputtering upon forming a thin film for the electrode.
Moreover, a target having a low sintering density has a drawback in that cracks and chips occur easily during the manufacturing process, operation or sputtering which result in decrease of the product yield, and, since the sputtering power cannot be increased during sputtering, the mass production cost deteriorates thereby.
In light of the above, there has been a proposal of adding a sintering auxiliary agent for increasing the sintering density. For example, the publication of Japanese Patent Laid Open Publication No. 2000-247739 describes an attempt of increasing the relative density to 85% to 90% by adding 0.001 mol % to 0.5 mol % of Bi2O3.
Nevertheless, even if the relative density is increased as described in the foregoing publication, the maximum relative density is still 90% or less, and it cannot be said that a satisfactory increase in the target density has been obtained.
Therefore, numerous particles are still generated during sputtering upon forming a thin film, and it has not been possible to effectively suppress the deterioration in quality and production yield heretofore.